Metallurgical apparatus



Jan. 23, 1934. J R MUNRO METALLURGICAL APPARATUS Filed April 1, 1931 2 Sheets-Sheet l I A INVENTOR.

James H. MUIVRO BY Jan. 23, 1934. R MUNRQ 1,944,449

METALLURGI CAL APPARATUS Filed April 1, 1931 2 Sheets-Sheet 2 FlgJiL INVENTOR.

James R. Mun/R0 A ORNEYS/M Patented Jan. 23, 1934 METALLURGICAL APPARATUS James R. Munro, San Leandro, Calif., assignor to Caterpillar Tractor 00., San Leandro, Calif., a corporation of California Application April 1, 1931.

Claims.

Statement of invention The invention relates to metallurgical apparatus. The object of the invention is to provide a metallurgical apparatus which will give more 5 accurate results, particularly as to temperature measurements and control.

Description of figures Fig. 1 is a sectional view of one type of furnace in which the invention is employed.

Fig. 2 is a sectional view of another type of furnace in which a modified form of the invention is employed.

Fig. 3 is a diagram.

Fig. 4 is a detailed view of part of the apparatus in Fig. 1.

Fig. 5 is a detailed view of part of the appa: ratus in Fig. 2.

Description of device The furnace illustrated in Fig. 1 is similar to that disclosed in application Serial No. 463,466, filed June 24, 1930. The material to be heattreated is placed in chamber 10. Heating units 11 are mounted on the outside of this chamber. An outer shield 12 together with the floor 13 and the roof 14 enclose the furnace and provide passage-way for air which is circulated by fan 15 as indicated by the arrows. The heat from the heating-units is transmitted to the material by convection.

A fuse 20 is positioned opposite one of the heating units 11 in order to control the temperature of-athe heating units. This fuse is constructed as shown in Fig. 4 and consists of two wires 21, 22, the ends of which are joined, by a drop of gold 23. These wires lead to a suitable controller for the heating unit circuit and when the temperature rises sufliciently to melt the gold the connection between wires 21, 22 is broken, thereby effecting through the controller the breaking of the heating unit circuit.

The end of the fuse is shielded by a refractory cup 24 and the wires are protected by refractory beads 25. The hood 24 shields the sensitive gold .spot 23 from the air current which would have a tendency to decrease its temperature, and since the open end of the hood is placed in close proximity with the heating unit, the temperature of 53 spot 23 is substantially the same as heating unit 11.

The thermocouple 30 is constructed in the same manner except that the wires are of different material and their ends are joined directly .-,3 together as illustrated, for example, in Fig. 5.

Serial No. 526,855

The hood 24 shields the sensitive point of the thermocouple, that is, the point at which the two wires are joined, from heat radiated from the heating units 11, so that the temperature of the thermocouple will be the temperature of' the air current at the open end of hood 24. The thermocouple is enabled to accuratelymeasure the temperature of the air leaving the heating units. without incurring serious error due to heat ra-' diated from the heating units themselves.

Thermocouple 30 can be connected to a controller to control the heating unit circuit to main tain the emperature of the air delivered to the charge within desired limits.

In Fig. 2 is illustrated a furnace such as that disclosed in application Serial No. 291,322, filed July 9, 1928, now Patent No. 1,825,059, granted to Walter Grothe, on September 29, 1931, which has a rotary annular hearth, only one half of the furnace being shown, the furnace being symmetrical about its vertical axis. The charge 40 is carried on the rotary annular hearth 41. Heating units 42 are mounted on the walls of the annular heating chamber 43. The thermocouple 50 is positioned over the charge. This thermocouple 80 is protected in somewhat the same fashion as that illustrated in Fig. 4. The cup-shaped shield 51 of refractory material protects the thermocouple which is obtained by welding together the ends of wires 52, 53 of different material at.54. Sensitive spot 54 is shielded on all sides but one, that side being the open end 55 of cup 51. Wires 52,

53 are protected by refractory beads 56.

By this arrangement thermocouple 50 accurately measures the temperature of the charge without being seriouly affected by heat radiated from the heating units.

A fuse 60 having its sensitive spot protected in the same manner is located with the open end of the cup opposite the heating units 42.

By these constructions it will be seen that the sensitive spot of either a thermocouple or a fuse sees" only the element whose temperature is to be measured or controlled thereby obtaining more accurate temperature measurements we and controlby shielding from sources of error. 1

I, therefore-claim as my invention:

1. A metallurgical furnace having walls forming a heating chamber in which the temperature 5 varies at different localities, a heated element positioned within said furnace, a heat detecting device mounted within said furnace, said heat detecting device having a heat sensitive portion adjacent said element but spaced therefrom, and 1 a shield enclosing said heat sensitive portion, said shield forming a walled enclosure defining a recess open only toward said element to allow heat radiated from said element to act on said heat sensitive portion, the walled portion of said shield projecting beyond said heat sensitive portion so that said heat sensitive portion is positioned within the outer edge of said walled portion and is protected from heat coming from localities both hotter and colder than the heat at the locality at which said element is positioned, whereby said heat sensitive portion is affected only by the heat from said element.

2. A metallurgical furnace having walls forming a heating chamber in which the temperature varies at different localities, a heated element positioned within said furnace, a heat detecting device including an elongated body portion of refractory material passing through a wall of said furnace and fixedly mounted therein, the inner end of said body portion terminating adjacent said element and being provided with a heat sensitive portion adjacent said element but spaced therefrom, and a shield of refractory material on the inner end of said body portion and enclosing said heat sensitive portion, said shield forming a walled enclosure defining a recess open only toward said element to allow heat radiated from said element to act on said heat sensitive portion, the walled portion of said shield projecting beyond said heat sensitive portion so that said heat sensitive portion is positioned within the outer edge of said walled portion and is protected from heat coming from localities both hotter and colder than the heat at the locality at which said element is positioned, whereby said heat sensitive portion is affected only by the heat from said element.

3. A metallurgical furnace having walls forming a heating chamber in which the temperature varies at different localities, a heated element positioned within said furnace and having a heat radiating surface lying in a plane, a heat detecting device including an elongated body portion of refractory material passing through a wall of said furnace and fixedly mounted therein, said elongated body portion being substantially parallel to said plane, the inner end of said body portion being provided with a heat sensitive portion adjacent said element but spaced therefrom, a cup-shaped shield of refractory material on the inner end of said body portion and enclosing said heat sensitive portion, the longitudinal axis of said shield extending substantially normal to said plane, said shield having a ,wall about said axis and a wall transverse to said axis defining a recess open only toward said element to allow heat radiated from said element to act on said heat sensitive portion, the walled portion of said shield projecting beyond said heat sensitive portion so that said heat sensitive portion is positioned within the outer edge of said walled portion and is protected from heat coming from localities both hotter and colder than the heat at the locality at which said element is positioned, whereby said heat sensitive portion is affected only by the heat from said element.

4. A metallurgical furnace having walls form-, ing a heating chamber in which the temperature varies at different locations, a plurality of heat detecting devices mounted within said furnace chamber each at a different location, each of said heat detecting devices having a heat sensitive portion, and a shield enclosing each heat sensitive portion, each of said shields forming a walled enclosure defining a recess open to receive the heat at the location of the heat sensitive portion, the walled portion of each shield projecting beyond said heat sensitive portion so that said heat sensitive portion is positioned within the outer edge of said walled portion and is protected from heat coming from all other locations, whereby each of said heat sensitive portions is only affected by the heat at the location thereof.

5. A metallurgical furnace having walls forming a heating chamber in which the temperature varies at different locations, a heated element within the furnace chamber at one location, another heated element within the furnace chamber at another location, a plurality of heat detecting devices mounted within said furnace, each of said devices being provided with a heat sensitive portion positioned adjacent one of said elements but spaced therefrom, and a shield of refractory material oneach device and enclosing the heat sensitive portion, each of said shields forming a walled enclosure defining a recess open only toward the element adjacent thereto to allow heat radiated from said element to act on said heat sensitive portion, the walled portion of each shield projecting beyond said heat sensitive portion so that said heat sensitive portion is positioned within the outer edge of said walled portion and is protected from heat coming from locations both hotter and colder than the heat at the location at which the element is positioned, whereby each of said heat sensitive portions is affected only by the heat from the element adjacent thereto.

JAMES R. MUNRO. 

